MCQS FOR MODULATION AND DEMODULATION USEFUL FOR B.Sc. STUDENTS

    1.     Modulation in which -

(a)    Some characteristics of carrier wave in accordance with intensity of the signal.

(b)    Signal is modified using carrier wave

(c)    carrier wave provide energy to signal

(d)    none of these

Ans.    (a)

2.    Modulation is done –

            (a)   in receiver                      

            (b) transmitter                       

            (c)  in receiver as well in transmitter

(d)    in amplifier

Ans. (b)

            3.     In India the modulation used in radio transmission is –

(a)   phase modulation                         

(b)  frequency modulation

(c)   amplitude modulation                   

(d) none of the above

Ans. (c)

              4.      In amplitude modulation useful power is contained in-

(a)   Carrier                            

(b)  side bands                                

(c) signal                         

(d) Both in carrier and sidebands

Ans. (b)

            5.     In amplitude modulation characteristics of carrier which changes in accordance with signal                     strength is –

(a)   frequency                          

(b)  phase                                     

(c) amplitude                  

(d) frequency and amplitude

Ans. (c)

            6.     Over modulation causes –

(a)   weakening of the signal

(b)   Strengthening of the signal

(c)   excessive power in carrier

(d)   distortion

Ans.   (d)

            7.     100%modulation may be achieved if –

(a)   signal amplitude is less than that of carrier

(b)   signal amplitude is greater than that of carrier

(c)   signal and carrier amplitudes are equal

(d)   modulator is efficient

Ans. (c)

8.    An A.M. wave is expressed as-

            V=5(1+0.6Cos6280t)Sin211× 10⁴ t volts

            the frequencies of lower and upper side band will be –

(a)   335 KHz and 337 KHz                                                 

(b)  336KHz and 337 KHz 

(c) 628KHz and 211KHz                                              

(d) 314KHz and 422KHz

Ans. (a)

            9.     If modulation factor (m) is for an an AM wave. percentage of total power of the wave contained             in side bands is

(a)   25%                       

(b) 40.5%                    

(c) 50%                       

(d) 33.3%

Ans. (d)

            10.     When modulating signal control the frequency of the carrier the resulting wave is –

(a)   amplitude modulated

(b)   phase modulated

(c)   frequency modulated

(d)   none of the above

Ans. (c)

            11.     Modulation is related to a low frequency signal controlling the-

(a)   amplitude of  the carrier

(b)   frequency of the carrier

(c)   phase of the carrier

(d)   any of the above

Ans. (d)

            12.     In a frequency modulated wave frequency deviation is 50KHz and modulation frequency is                 5KHz  modulation index (ms)  is –

(a)   5                            

(b)10                           

(c)15                           

(d)15

Ans. (b)

           13.     Band width required to transmit an audio signal of 2KHz.The carrier frequency  is 500 KHz is -

(a)   4KHz                    

(b) 496khz                              

(c) 504KHz                  

(d)  502KHz

Ans. (a)

14.     Derive  which separate out the signal from modulation the signal form modulated wave is-

(a)   transmitter            

(b) detector                             

(c) filter                 

(d)amplifier

Ans. (b)

            15.     Amplitude of a carrier is mode to vary between 150and 40V. The modulation factor is-

(a)   0.3                         

(b)0.6                          

(c) 0.55                        

(d) 0.65

Ans. (b)